When a neuron becomes depolarized, what ion is responsible for this and what direction does in move (in relation to the cell) ?

Sodium ion (Na+) is responsible for depolarization and it enters the cell, direction is fr m the outside in

Explanation:

In a resting membrane of a cell, there are more sodium ions (Na+) outside the neuron and more potassium ions (K+) inside that neuron. The resting potential is the state of the membrane at a voltage of - 70 mV.

Therefore, when a channel opens for Na + in the membrane the ions move inside the cell because the concentration of Na + is higher outside the cell than inside the cell by a factor of 10 as a result of the concentration gradient. This will change the relative voltage immediately inside the cell relative to immediately outside, so the sodium cation entering the cell will cause it to become less negative resulting in depolarization